Sunny Goyal
70 lines
2.5 KiB
Java
70 lines
2.5 KiB
Java
package com.android.launcher3.allapps;
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import android.content.res.Resources;
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import android.graphics.Outline;
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import android.support.v7.widget.RecyclerView;
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import android.view.View;
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import android.view.ViewOutlineProvider;
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import com.android.launcher3.BaseRecyclerView;
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import com.android.launcher3.R;
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import com.android.launcher3.Utilities;
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/**
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* Helper class for controlling the header elevation in response to RecyclerView scroll.
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*/
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public class HeaderElevationController extends RecyclerView.OnScrollListener {
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private final View mHeader;
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private final float mMaxElevation;
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private final float mScrollToElevation;
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private int mCurrentY = 0;
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public HeaderElevationController(View header) {
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mHeader = header;
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final Resources res = mHeader.getContext().getResources();
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mMaxElevation = res.getDimension(R.dimen.all_apps_header_max_elevation);
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mScrollToElevation = res.getDimension(R.dimen.all_apps_header_scroll_to_elevation);
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// We need to provide a custom outline so the shadow only appears on the bottom edge.
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// The top, left and right edges are all extended out, and the shadow is clipped
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// by the parent.
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final ViewOutlineProvider vop = new ViewOutlineProvider() {
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@Override
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public void getOutline(View view, Outline outline) {
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final View parent = (View) mHeader.getParent();
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final int left = parent.getLeft(); // Use the parent to account for offsets
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final int top = view.getTop();
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final int right = left + view.getWidth();
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final int bottom = view.getBottom();
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final int offset = Utilities.pxFromDp(mMaxElevation, res.getDisplayMetrics());
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outline.setRect(left - offset, top - offset, right + offset, bottom);
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}
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};
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mHeader.setOutlineProvider(vop);
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}
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public void reset() {
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mCurrentY = 0;
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onScroll(mCurrentY);
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}
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@Override
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public final void onScrolled(RecyclerView recyclerView, int dx, int dy) {
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mCurrentY = ((BaseRecyclerView) recyclerView).getCurrentScrollY();
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onScroll(mCurrentY);
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}
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private void onScroll(int scrollY) {
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float elevationPct = Math.min(scrollY, mScrollToElevation) / mScrollToElevation;
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float newElevation = mMaxElevation * elevationPct;
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if (Float.compare(mHeader.getElevation(), newElevation) != 0) {
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mHeader.setElevation(newElevation);
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}
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}
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}
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